Operation Manual – QoS-QoS Profile
H3C S5600 Series Ethernet Switches
Chapter 1 QoS Configuration
1-11
Token
bucket
Drop
Packet
classification
Packets to be sent
through this port
Continue
to send
Put tokens in the bucket at the
set rate
Figure 1-5
Evaluate the traffic with the token bucket
II. Evaluating the traffic with the token bucket
When token bucket is used for traffic evaluation, the number of the tokens in the token
bucket determines the amount of the packets that can be forwarded. If the number of
tokens in the bucket is enough to forward the packets, the traffic is conforming to the
specification; otherwise, the traffic is nonconforming or excess.
Parameters concerning token bucket include:
z
Average rate: The rate at which tokens are put into the bucket, namely, the
permitted average rate of the traffic. It is generally set to committed information
rate (CIR).
z
Burst size: The capacity of the token bucket, namely, the maximum traffic size that
is permitted in each burst. It is generally set to committed burst size (CBS). The set
burst size must be greater than the maximum packet length.
One evaluation is performed on each arriving packet. In each evaluation, if the number
of tokens in the bucket is enough, the traffic is conforming to the specification and you
must take away some tokens whose number is corresponding to the packet forwarding
authority; if the number of tokens in the bucket is not enough, it means that too many
tokens have been used and the traffic is excess.
III. Traffic policing
The typical application of traffic policing is to supervise specific traffic into the network
and limit it to a reasonable range, or to "discipline" the extra traffic. In this way, the
network resources and the interests of the operators are protected. For example, you
can limit HTTP packets to be within 50% of the network bandwidth. If the traffic of a
certain connection is excess, traffic policing can choose to drop the packets or to reset
the priority of the packets.
